Body frame for motorcycle

Abstract

A body frame for a motorcycle includes a main frame having a reinforcing member, which is a forged product, and a portion that requires a high strength against a shock load transmitted from a road surface. A pair of sidewalls and a connecting wall for connecting the sidewalls are also provided. The sidewalls create spaces opened outward in cross-section such that the connecting wall has an external face positioned in the portion that requires high strength.

1. A body frame for a motorcycle comprising:
 a down frame member having sidewalls and a single connecting wall that connects the sidewalls to define a space opened upward in cross-section, wherein an external face of the connecting wall faces downward; 
 a tank rail member having a C-shape in cross-section; and 
 gussets defining vertical walls that connect the sidewalls of the down frame member with the tank rail member. 
 
   
   
     2. The body frame of  claim 1 , further comprising a head pipe for supporting a front fork, wherein:
 the gussets extend obliquely downward from the head pipe while widening in a rearward manner. 
 
   
   
     3. The body frame of  claim 2 , wherein:
 the down frame member comprises a lower head connected to a lower end of the head pipe and having a bearing seat, and 
 the down frame member extends from the lower head and the sidewalls of the down frame member cover and are jointed to lower edges of the vertical walls of the gussets from below. 
 
   
   
     4. The body frame of  claim 2 , wherein:
 the tank rail member has sidewalls and a single connecting wall that connects the sidewalls to define a space opened downward in cross-section, wherein an external face of the connecting wall faces upward, 
 the tank rail member further comprises an upper head connected to an upper end of the head pipe and having a bearing seat, and 
 the tank rail member extends from the upper head and the sidewalls of the tank rail member cover and are jointed to upper edges of the vertical walls of the gussets from above. 
 
   
   
     5. The body frame of  claim 1 , and further comprising:
 rear cushion brackets formed integrally with and extending from rear portions of the gussets. 
 
   
   
     6. The body frame of  claim 2 , wherein:
 the tank rail member extends obliquely downward and rearward from a top portion of the head pipe; 
 the down frame member extends obliquely downward and rearward from a bottom portion of the head pipe; 
 a pair of left and right down tubes extend rearward from a rear end of the down frame member; and 
 a pair of left and right rear arm brackets connect rear ends of the down tubes and a rear end of the tank rail member, and support rear arms in a manner to permit the rear arms to move in an up and down swinging motion. 
 
   
   
     7. The body frame of  claim 6 , wherein each rear arm bracket has an approximately U-shaped cross-section comprising front and rear sidewalls extending from front and rear edges of a vertically extending connecting wall. 
   
   
     8. The body frame of  claim 7 , wherein inwardly facing external faces are defined on upper portions of the connecting walls of the rear arm brackets adjacent the connections with the tank rail member. 
   
   
     9. The body frame of  claim 8 , wherein outwardly facing external faces are formed on lower portions of the connecting walls of the rear arm brackets adjacent the connections with the down tubes. 
   
   
     10. The body frame of  claim 6 , wherein lower portions of the rear arm brackets are connected by an extruded angular cylindrical cross pipe, and wherein a work hole is formed through the cross pipe to receive a fastening bolt for change pedals. 
   
   
     11. The body frame of  claim 6 , wherein:
 a rear end of the down frame member has receiving portions formed with rearward-facing mounting openings; 
 lower ends of the rear arm brackets have receiving portions formed with forward-facing mounting openings; 
 front ends of the down tubes are received in and welded to the receiving portions of the rear end of the down frame member; and 
 rear ends of the down tubes are received in and welded to the receiving portions of the lower ends of the rear arm brackets. 
 
   
   
     12. A motorcycle comprising the body frame of  claim 1 . 
   
   
     13. A body frame for a motorcycle comprising:
 a head pipe; 
 a first reinforcing member extending rearward from a lower end of the head pipe and comprising sidewalls connected by a single connecting wall to define a space opened upward in cross-section, an external face of the connecting wall facing downward; 
 a second reinforcing member extending rearward from an upper end of the head pipe and comprising sidewalls connected by a single connecting wall to define a space opened downward in cross-section, an external face of the connecting wall facing upward; and 
 gussets comprising vertical walls connecting the sidewalls of the first reinforcing member with the sidewalls of the second reinforcing member, wherein the sidewalls of the first reinforcing member are welded to and cover lower edges of the vertical walls of the gussets, and the sidewalls of the second reinforcing member are welded to and cover upper edges of the vertical walls of the gussets. 
 
   
   
     14. The body frame of  claim 13 , wherein:
 the first reinforcing member is a down frame member having a U-shaped cross-section; and 
 the second reinforcing member is a tank rail member having a C-shaped cross-section. 
 
   
   
     15. The body frame of  claim 13 , and further comprising:
 a pair of down tubes extending rearward from a rear end of the first reinforcing member; and 
 third reinforcing members connecting rear ends of the down tubes and a rear end of the second reinforcing member, and being configured to support rear arms that move in an up and down swinging motion. 
 
   
   
     16. The body frame of  claim 15 , wherein each third reinforcing member has an approximately U-shaped cross-section comprising front and rear sidewalls extending from front and rear edges of a vertically extending connecting wall. 
   
   
     17. The body frame of  claim 16 , wherein:
 inwardly facing external faces are defined on upper portions of the connecting walls of the third reinforcing members adjacent the second reinforcing member; and 
 outwardly facing external faces are formed on lower portions of the connecting walls of the third reinforcing members adjacent the down tubes. 
 
   
   
     18. A motorcycle comprising the body frame of  claim 13 .